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Commit a9f3e2b5 authored by Mike Galbraith's avatar Mike Galbraith Committed by Ingo Molnar
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sched: clear buddies more aggressively 



It was noticed that a task could get re-elected past its run quota due to buddy
affinities. This could increase latency a little. Cure it by more aggresively
clearing buddy state.

We do so in two situations:
 - when we force preempt
 - when we select a buddy to run

Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 1596e297

kernel/sched_fair.c

+12 −1
Original line number Diff line number Diff line
@@ -768,8 +768,14 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) 


	ideal_runtime = sched_slice(cfs_rq, curr);

	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;

	if (delta_exec > ideal_runtime)

	if (delta_exec > ideal_runtime) {

		resched_task(rq_of(cfs_rq)->curr);

		/*

		 * The current task ran long enough, ensure it doesn't get

		 * re-elected due to buddy favours.

		 */

		clear_buddies(cfs_rq, curr);

	}

}



static void
@@ -1445,6 +1451,11 @@ static struct task_struct *pick_next_task_fair(struct rq *rq) 


	do {

		se = pick_next_entity(cfs_rq);

		/*

		 * If se was a buddy, clear it so that it will have to earn

		 * the favour again.

		 */

		clear_buddies(cfs_rq, se);

		set_next_entity(cfs_rq, se);

		cfs_rq = group_cfs_rq(se);

	} while (cfs_rq);